The field of the present invention is semiconductor thyristors in which portions of the emitter are shunted by portions of the base region extending through the emitter into contact with the emitter electrode.
The shunt of a known thyristor of the aforementioned type is formed by the emitter electrode itself, which on its side facing away from the control electrode extends over the emitter, and is connected to the base. A shunt of this kind has proved advantageous from the electric viewpoint in the case of small-area thyristors having an effective emitter area of, e.g., less than 10 mm.sup.2. The strip-shaped control electrode, in association with the aforementioned shunt is also highly suitable for the economical production of the aforementioned small-area thyristors. In a known process of this type, to this end a large-area semiconductor element is provided with a number of parallel, metallized strips for the control electrodes and with a number of wider, parallel strips for the emitter electrodes. Here, the metal strips provided for the emitter electrodes are arranged on the emitter of the large-area semidconductor element, and the metal strips provided for the control electrodes are arranged on portions of the base of this semiconductor element, which appear in the form of strips at the surface of the semiconductor element. The large-area semiconductor element is divided up into small-area semiconductor elements by a number of parallel cuts which divide up the base and emitter electrodes in the longitudinal direction, and by a number of cuts running at right angles to the former.
When the described process is also used for larger thyristors, the use of a strip-shaped shunt is limited at effective emitter areas of over 10 to 15 mm.sup.2, if utilizable du/dt values are to be obtained. The widening of the shunt provides only a limited remedy, as a large part of the emitter surface with an increasing area of the thyristor, comes to lie too far from the shunt for the latter to still exert any effect. In the case of thyristors having a larger emitter area, therefore, one employs cylindrical openings which are arranged in the emitter surface and through which the base extends to the emitter electrode and is electrically connected to the latter. For the simple production of the thyristors, generally a regular arrangement of the shunts is selected. In the case of radial-symmetrical thyristors the shunts can be arranged regularly on concentric circles or otherwise. In the case of thyristors whose semiconductor elements are produced by cutting up a large-area semiconductor element, an arrangement consisting of columns and rows will be selected.
However, during the division of the large-area semiconductor element, it can occur that as a result of inaccurate cutting, entire columns or rows of shunts will be lost. The outcome will be all the more drastic, the more area space occupied by the individual shunt.